The invention relates generally to imaging systems and more specifically to a method and system for acquiring images.
Many industrial inspection systems require very high detection efficiency, excellent signal-to-noise performance and coverage. In addition, it is desired that the overall cost of the industrial system is reasonable.
Linear detection arrays may be used for various low energy and high-energy x-ray inspection applications. Such detector arrays receive X-rays emitted by a source and passing through an object that is required to be scanned. Typically such arrays have limited flexibility as the detectors generally involve fixed geometry configurations.
Typically, such detectors include a scintillator layer and a photoconversion device. The photoconversion device has many photosensor elements. The photosensor elements are arranged based on one or more pre-determined paths that the X-rays follow. FIG. 1 is a block diagram of a conventional X-ray inspection system. X-ray source 10 generates an X-ray beam with X-ray paths 7, 8 and 9 respectively. The photosensor elements 6 are aligned with respect to the respective X-ray paths. Thus, for a particular source-to-detector distance (SDD), photosensor elements are focally aligned with the respective X-ray path.
Current X-ray inspection methods typically produce spectrum dependent information by performing two or more different scans, where each scan is achieved with a particular voltage setting of an industrial x-ray tube, typically in conjunction with an energy-integrating detector. Another method is to use a detector with two or more separate distinct layers in succession of the same or different, attenuating materials.
In a multi-layer approach, lower energy X-rays tend to be attenuated in the first layer, and higher energy X rays tend to penetrate through to and be attenuated by the second layer. Another method is to use a photon counting detector which produces an amplitude spectrum of absorbed energy and which can be binned in energy to provide energy separation. All of these methods, generally referred to as energy discrimination, allow the extraction of information on material-specific constituents, rather than information on electron density provided by energy-integrating detectors.
It may also be required that inspection systems be configured to identify and/or quantify specific materials in an object, which is particularly useful in several nondestructive testing and security inspection applications. However, a conventional inspection image data set, produced with a single source spectrum and an energy-integrating detector, permits only the extraction of information on material density. Usually, little information on the amounts of specific materials can be extracted from these conventional image data sets.
Therefore, there is a need to design detectors that are capable of scanning various arbitrary geometries for different source to detector distances, while maintaining high x-ray detection efficiency, spatial resolution and material-specific detection capability.